(a) Field of the Invention
The present invention relates to apparatus for assembling rotors for forming inscribe-type gear pump in such a manner as to incorporate an inner rotor having a gear portion around its outer periphery into an outer rotor having a gear portion around its inner periphery.
(b) Description of Prior Art
As shown in FIG. 13, an inscribe-type gear pump in non-crescent configuration has been conventionally formed in such a manner as to eccentrically incorporate an inner rotor 4 having a gear portion around its outer periphery into an outer rotor 2 having a gear portion 1 around its inner periphery. In the inner rotor 4 are provided a central hole 5 and peripheral holes 6 in cylindrical configuration to be connected to a driving axis. Said central hole 5 penetrates through the central axis portion of a inner rotor 4, and peripheral holes 6 are positioned around said central hole 5, surrounding said central hole 5 axially in parallel. Both an outer rotor 2 and an inner rotor 4 are incorporated into a casing having an inlet port 7 and an outlet port 8 respectively, with the former being opposite to the latter on a diameter passing through eccentric axes of both rotors. The rotation drive of said inner rotor 4 allows said outer rotor 2 to rotate, so that oil sucked from an inlet port 7 is delivered to an outlet port 8, passing through the space between said outer rotor 2 and said inner rotor 4. Both rotors are manufactured, for instance, by compressing powdered material mainly composed of metal to be molded, and thereafter, heating and sintering it.
In the past, outer rotors 2 and inner rotors 4 have been shipped separately. Accordingly, as relatively a large packing capacity is inevitably needed, and both rotors are finally to be used with one into the other, so that both rotors have come to be shipped in said incorporated state after having manufactured outer and inner rotors respectively. In such cases, each inner rotor 4 has been conventionally incorporated one by one into each outer rotor 2 in a manual manner, which takes time, is laborious lowers efficiency and increases cost. A prior device is disclosed for overcoming this problem, such as grasping means for assembling parts having openings therein, as shown in U.S. Pat. No. 4,630,344, which discloses apparatus for assembling different size parts in a vertical assembly, including a pair of fingers attached to and extending from the gripper of a manipulator in parallel relationship and movable toward and away from one another under control of the gripper. However, this patent cannot be utilized to assemble rotors that require rotating means to engage.
Therefore, rotor assembling apparatus for automatically incorporating an outer rotor 2 into an inner rotor 4 is to be invented. The inventor is inevitably to be confronted with the problem of how to engage a gear portion 3 of an inner rotor 4 with a gear portion 1 of an outer rotor 2. One solution is to incorporate said inner rotor 4 into said outer rotor 2 after having located said inner rotor 4 in an appropriate position on the periphery, by means of an optical sensor to detect the appropriate position of the gear portion 3 of said inner rotor 4. But in the above-mentioned method, the installed position of said sensor will be limited, so that such rotor assembling apparatus will be inevitably too expensive in addition to its complex construction. Furthermore, as the largest clearance "c" between the top-most vertices of said gear portions 1,3 is formed approximately 0.05 mm long to prevent oil leakage, only a little error of positioning can cause the interference of said gear portion 1 with said gear portion 3. Consequently, an inner rotor 4 cannot be incorporated into an outer rotor 2.